1. Field of the Invention
The invention relates to a system for transmitting a binary source signal from a data transmitter to a data receiver through a noisy dispersive channel introducing intersymbol interference, wherein the data transmitter has a sliding block encoder which converts the binary source signal at a given symbol rate 1/T into an encoded binary data signal at a symbol rate P/(NT), where P and N are positive integers such that N/P.ltoreq..sup.2 log(3)/2=0.79248; and the binary source signal at the symbol rate 1/T is reconstructed in the data receiver.
2. Description of the Related Art
Such a system is known from an article `Recording Codes for Digital Magnetic Storage` by P. H. Siegel, IEEE Trans. Magn., Vol. MAG-21, No. 5, pp. 1344-1349, 1985, and in particular FIGS. 1 and 2 of this article. In what follows, the transformation by the sliding block encoder of the the binary source signal at the symbol rate 1/T into the encoded binary data signal at the symbol rate P/(NT) will be referred to as a binary modulation code for the sake of brevity.
In systems of said type, the reconstruction circuit commonly consists of a memoryless detector in cascade with a decoder. The equalizer, sampler and detector are then used to reconstruct the encoded binary data signal at the symbol rate P/(NT), from which the binary source signal at the symbol rate 1/T is recovered by means of the decoder. According to this approach, the receiver largely operates at an oversampling factor of P/N with respect to the binary source signal at the symbol rate 1/T. For typical values of P/N of like 2 or 3/2, this oversampling may pose instrumentational problems when the symbol rate 1/T is high. To reduce such problems, it is desirable for the receiver to operate entirely without oversampling.
Such a possibility is known for the MFM modulation code, as described in said article by Siegel. For this code with P=2 and N=1, sampling may occur at the symbol rate 1/T, and the equalizer should then be dimensioned for its sampled output signal to resemble as well as possible a linearly transformed and decimated version of the encoded data. This yields an essentially ternary signal at the symbol rate 1/T, from which the binary source signal can be directly recovered by means of a detector without memory.